1. Field of the Invention
The present invention relates to high frequency dielectric ceramic compositions and relates to dielectric resonators, dielectric filters, dielectric duplexers and communication apparatuses using said compositions.
2. Description of the Related Art
Dielectric ceramics have been widely used as materials for dielectric resonators, dielectric filters and circuit substrates in electronic equipment, for example, cellular phones, personal radios and satellite broadcasting receivers utilizing high frequencies such as microwaves and milliwaves.
Dielectric properties required of such high frequency dielectric ceramic compositions are preferably:
(1) the relative dielectric constant (∈r) is large in order to respond to the requirement for miniaturization because the wavelength of electromagnetic wave is shortened to 1/(∈r)1/2 in the dielectric,
(2) dielectric loss is small, or Q value is large, and
(3) temperature stability of resonant frequency is superior, or temperature-dependent factor of resonant frequency (xcfx84f) is close to 0 (ppm/xc2x0C.).
As these types of dielectric ceramic compositions, Ba(Zn,Ta)O3 series (Japanese Examined Patent Application Publication No. 58-25068), Ba(SN,Mg,Ta)O3 series (Japanese Examined Patent Application Publication No. 3-34164), (Zr, Sn)TiO4 series (Japanese Examined Patent Application Publication No. 4-59267), Ba2Ti9O20 (Japanese Unexamined Patent Application Publication No. 61-10806) and other dielectric ceramic compositions have been disclosed.
However, materials of the Ba(Zn,Ta)O3 series and the Ba(SN,Mg,Ta)O3 series have very large Q values of 150,000 to 300,000 at 1 GHz but have relatively small relative dielectric constants (∈r) of 24 to 30.
Materials of the (Zr,Sn)TiO4 series and the Ba2Ti9O20 series have relatively large relative dielectric constants (∈r) of 37 to 40 and large Q values of 50,000 to 60,000 at 1 GHz, but it is difficult to realize larger relative dielectric constants (∈r) of, for example, more than 40.
In recent years, requirements for loss minimization and miniaturizing of electronic equipment have been intensified. Accompanying this, regarding dielectric materials, requirements for developing materials having further superior dielectric properties, especially both large relative dielectric constants (∈r) and large Q value, have been intensified. Such requirements, however, have not been met up until now.
Accordingly, it is an object of the present invention to provide high frequency dielectric ceramic compositions having a relative dielectric constant (∈r) of 30 to 50, Q values of 15,000 or more at 1 GHz, and temperature-dependent factors of resonant frequency (xcfx84f) which can be arbitrarily controlled centering around 0 (ppm/xc2x0C.). It is another object of the present invention to provide dielectric resonators, dielectric filters, dielectric duplexers and communication apparatuses using the compositions.
To achieve the aforementioned objects, a high frequency dielectric ceramic composition of the present invention is characterized in including a rare earth element (Ln), Ma which is at least one selected from the group consisting of Mg and Zn, Mb which is at least one selected from the group consisting of Sn and Zr, and Ti and Me which is at least one selected from the group consisting of Ca and Sr, the dielectric ceramic having a composition shown by the formula
(1xe2x88x92x)MeTiaO1+2axe2x80x94xLn(Ma1/2Mb1/2)bO(3+3b)/2,
wherein x is the mole fraction and a, b, and x are within the ranges 0.950xe2x89xa6axe2x89xa61.050, 0.900xe2x89xa6bxe2x89xa61.050, and 0.300xe2x89xa6xxe2x89xa60.500, and the dielectric ceramic having a main crystal of the perovskite type crystal phase.
The aforementioned rare earth element (Ln) may be at least one selected from the group consisting of Y, La, Pr, Nd and Sm.
The aforementioned Me may be Ca, and the aforementioned Ma may be Mg.
A dielectric resonator of the present invention is actuated by the electromagnetic connection of input/output terminals and a dielectric ceramic is characterized in that the dielectric ceramic is composed of a high frequency dielectric ceramic composition of the present invention.
A dielectric filter of the present invention is characterized in being composed of the aforementioned dielectric resonator including an outer connection unit.
A dielectric duplexer of the present invention including at least two dielectric filters, input/output connection units connected to each dielectric filter, and an antenna connection unit commonly connected to the dielectric filters is characterized in that at least one of aforementioned dielectric filters is a dielectric filter of the present invention.
A communication apparatus of the present invention is characterized in including a dielectric duplexer of the present invention; a transmitting circuit connected to at least one input/output connection unit of the dielectric duplexers; a receiving circuit connected to at least one input/output connection unit which is different from said input/output connection unit connected to the transmitting circuit; and an antenna connected to the antenna connection unit of the dielectric duplexer.